Strictly speaking, these are not defined. Infinity isn't a number like any other. As some people have noted, there are a number of different sizes (more properly cardinalities) of infinity. But even within one cardinality, it's undefined.
Supposing I have a vat, filled with infinite ping-pong balls, and for any natural number (i.e. 1, 2, 3, 4...), the vat contains precisely one ping-pong ball labeled with that number. I also have another vat, this one containing a labeled ping-pong ball for every integer, positive or negative. Clearly, I can reach into the second vat, and pull out an infinite number of ping-pong balls without a mate in the first vat: if I pull out -1 from the second vat, no matter how long I search, I will never find a ping-pong ball labeled -1 in the first vat.
Yet I claim that the two vats contain the same number of balls. Supposing I match them up differently. Every ping-pong ball in the first vat labeled with an even number n gets matched to the ping-pong ball in the second vat labeled with n/2, and every odd numbered ping-pong ball in the first vat gets matched to the ball in the second vat labeled -((n-1)/2). Thus, for every ball in the second vat, I can remove a corresponding ball from the first vat. The two vats must be the same size.